1. Field of the Invention
The present invention relates to a method of manufacturing a resin-encapsulated semiconductor device, and a lead frame. In particular, the present invention relates to a method of removing a resin burr of a resin-encapsulated semiconductor device and a metal adhered thereto.
2. Description of the Related Art
In recent years, in order to respond to miniaturization of electronic equipment, high-density mounting of electronic devices to be loaded in the electronic equipment has been demanded. The electronic devices include a resin-encapsulated device in which a chip having an element such as a transistor mounted thereon is encapsulated in an encapsulation resin together with a wiring member such as a lead. Also the resin-encapsulated device is becoming miniaturized and thinned. Along therewith, the pitch of the leads in the resin-encapsulated device is becoming reduced, and a method of mounting the electronic devices tends to be diversified as exemplified by the appearance of leadless devices. To deal with this, a novel manufacturing method involving the mounting of electronic devices has been sought after.
The structure of a related-art encapsulated semiconductor device and a manufacturing method therefor are described below.
FIG. 6 is a plan view of a lead frame to be used for manufacturing a related-art resin-encapsulated semiconductor device. A related-art lead frame 40 includes a quadrangular outer frame, a quadrangular die pad 21 for mounting a semiconductor chip thereon, a suspension lead 25 for connecting the outer frame and the die pad 21 to each other, an inner lead 23, and an outer lead 24. The die pad 21 is provided substantially at a center part of a region surrounded by the outer frame. The inner lead 23 is electrically connected to the semiconductor chip via connection means such as a thin metal wire in the state in which the semiconductor chip is mounted. The outer lead 24 is provided continuously to the inner lead 23 and is used for connection to an external terminal. A plurality of leads 22 are coupled to one another via a tie bar 32. A metal plating layer 28 made of silver or the like is selectively coated on the die pad 21 and the inner lead 23 of the lead 22. Further, a part surrounded by the dotted line is a region to be encapsulated by an encapsulation resin 31. Note that, the lead frame 40 does not have only one independent pattern formed of the structure illustrated in FIG. 6, but has a plurality of patterns arranged continuously in the horizontal and vertical directions of FIG. 6 for high volume manufacturing.
FIG. 7 is a perspective plan view of the related-art resin-encapsulated semiconductor device. A semiconductor chip 26 is mounted on the die pad 21 of the lead frame 40 illustrated in FIG. 6. Electrodes (not shown) on a surface of the semiconductor chip 26 are connected to the inner leads 23 via thin metal wires 27. The semiconductor chip 26, the thin metal wires 27, and the like are encapsulated by the encapsulation resin 31 so that the outer leads 24 may be exposed. In FIG. 7, the encapsulation resin 31 is transparent. An adhered metal 34 is present between the outer leads 24, which is a part of metal that is scattered when the lead frame is heated and melted with the use of a laser for removing the tie bar 32 and removing a resin protruding in resin encapsulation. Such an adhered metal is highly responsible for an electrical characteristics failure. To avoid this, the following method has been proposed. In a laser cutting step, a tape material is brought into close contact with a cutting portion so that a part of melted metal may be transferred onto the tape material, thereby preventing the melted metal from adhering on a product region (see, for example, Japanese Published Patent Application H11-260982).
The above-mentioned manufacturing method, however, has a concern about an increase in manufacturing cost because of the additional step of attaching and removing the tape member.